This interesting circuit uses a sodion valve that we have already described in an article on the website. The circuit uses several batteries for power. The phone is of high impedance.
This simple CMOS touch switch with bistable action must not be powered by a source without a...
This one-transistor alarm can be used with much more sensors than the two shown by the figure....
This circuit was suggested by Sprague Electric in an 80's documentation. The circuit uses a...